1. Technical Field
The present invention relates to a method for producing water-repellent treated aluminum pigment dispersion, a water-repellent treated aluminum pigment, and an aqueous ink composition containing the pigment.
2. Related Art
As a method for forming a coating having metallic gloss on a printed matter, it has been employed, for example, foil stamping printing using a printing ink including a gold or silver powder made from, for example, brass or aluminum fine particles or metallic foil, or a thermal transfer system using metallic foil.
Recently, there have been many applications of ink jet technology to printing. Metallic printing is one of such applications, and ink having metallic gloss has been being developed. For example, JP-A-2008-174712 discloses an aluminum pigment dispersion containing an organic solvent such as alkylene glycol as a base material and discloses a non-aqueous ink composition containing the dispersion.
At the same time, it is the current status that aqueous ink compositions are required to be developed, rather than non-aqueous ink composition containing organic solvents as base materials, from the viewpoints of global environment and safety for the human body.
However, an aluminum pigment has a problem that the pigment dispersed in water reacts with water to generate hydrogen gas and also form alumina, resulting in whitening to impair the metallic gloss. Therefore, the base material of an ink composition containing an aluminum pigment must be an organic solvent hardly containing water.